Several plant from the Apocynaceae, provides many top - level drugs: reserpine, ajmaline, strophantine, vinblastine etc ...
Apocynaceae plants contain a lot of alkaloids ; all have not been studied if not described; many are too toxic to be used in human therapy but can serve as a chemical (structural) basis for finding new, less harmful or more effective molecules.
Alkaloids used to fight cancers and leukemia ,therefore having a cytostatic or oncolytic action, are the most sought after and this following the discovery around 1960 of two very effective molecules in the Madagascar periwinkle (vincristine and vinblastine).
Catharantus roseus is à small flowering plant, probably native to the Indian Ocean, widespread in all intertropical regions; it is a perennial sub-shrub whose simple and discreet flowers are pink, mauve or white.
Madagascar periwinkle is mostly used in tropical and subtropical regions for ornamental purposes, it is very decorative in flowerbeds.
it is a particularly resistant plant which adapts to poor, sandy soils, very sunny but does not support the cold.
Traditionally Madagascar periwinkle has long been known as a drug to cure diabetes and hypertension.
VINBLASTINE AND VINCRISTINE
It is by screening the many potentially active alkaloids (around 90) of Catharantus roseus that two particularly active molecules were isolated:
leurocristine = vincristine
and vincaleucoblastine = vinblastine.
The aerial part of periwinkle contains 0.2% to 1% alkaloids and the rate of vincristine, the rarer of the two alkaloids, is only 0.0003% or 3g per 1 ton of dry matter !!
These are dimeric alkaloids combining two indole subunits.
They are ANTIMITOTIC by cytostatic effect, and also oncolytic, by a partially elucidated mechanism: they block cell reproduction by acting on the microtubules of the spindle, blocking mitosis at the metaphase stage; in vitro they are also inhibitors of the biosynthesis of proteins and nucleic acids.
These “cellular poisons” unfortunately have side effects, in particular on the nervous system, by acting on the microtubules of the axons, hence their neurotoxicity.
OTHER PROPERTIES SOMETIMES OBSOLETE
The anti-diabetic properties of Catharantus roseus have not been clinically confirmed.
3 alkaloids are hypoglycemic but effective at doses which make the phytomedicine toxic because of the other indole compounds.
The dried root is a source of AJMALICINE = RAUBASINE (also extracted from rauwolfias).
It is an alpha blocking spasmolytic which opposes the effects of adrenaline (adrenolytic) and increases cerebral blood flow (up to 30% of carotid flow) thus ensuring better irrigation of the brain.
Raubasine also shows an affinity for benzodiazepine receptors and thus exhibits a slight ANXIOLYTIC and anticonvulsant activity.
USES
TRADITIONAL MEDICINE
Traditionally, a leaf decoction is used :
Example, 40g in 1 liter of water, one cup morning and evening
This alkaloid "cocktail" is traditionally recommended to lower blood pressure and as an antidiabetic (perhaps by an anorectic effect= decreasing appetite) but lacks clinical verification.
In the West Indies it is prescribed as a gargle (angina) and the crushed leaves are used as a plaster on bruises .
CANCER THERAPY
VINBLASTINE AND VINCRISTINE extracted from the Madagascar periwinkle are two major antimitotics (hodgkin's disease, lymphoma, sarcoma, mammary carcinoma, lung cancer etc.) used alone or in combination with other antimitotics.
NOTE : An infusion-decoction or an alcoholic tincture of madagascar periwinkle do not contain enough alcaloids to cure cancer or leukemia.
OTHER USES (OBSOLETE)
AJMALICINE = raubasine enters into the composition of drugs intended to improve the cerebral function of the elderly, psychic disorders of senescence, often following vascular-cerebral accidents (ischemia, spasms, traumatisms, surgery).
Various sensory disorders are also a good indication: retinopathy of vascular origin, inner ear disorder (dizziness and tinnitus).
This plant so discreet, so widespread and so common in the tropics is in fact a powerful therapeutic agent.
Catharantus roseus, Madagascar periwinkle a tropical plant to fight cancer and leukemia
This small flowering plant native to the Indian Ocean is perennial in the tropics
and annual in temperate regions.
It contains many active substances which are very important in medicine (alkaloids)
, some of which are anticancer and antileukemic.
Other compounds improve the cerebral functions of elderly subjects, for example memory or hearing disorders, the consequences of cerebrovascular accidents: stroke, hemorrhages.
Copyright 2020 : Dr Jean-Michel Hurtel
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